Re: XMS memory

["Milton D. Miller II" <miltonm@bga.com>]

        From mailfail@UCSD.EDU Sat Apr 22 23:02:39 1995
        Date: Sun, 23 Apr 95 02:28:00 -0000
        From: mikebw@bilow.bilow.uu.ids.net (Mike Bilow)
        Subject: XMS memory
        To: TCP-Group@UCSD.EDU
        Reply-To: mikebw@bilow.bilow.uu.ids.net

Mike Bilow wrote:

B>Klarsen wrote in a message to Mike Bilow:
B>
B> K>   This is not new but wish to bring it to light again. I
B> K> was making  a large version of jnos 1.10i and saw in
B> K> config.h that XMS memory can not  be used.
B>
B>Correct.
B>
B> K>   Since I run Windows it is counter-productive to use EMS.
B> K> The EMS  driver cannot be loaded high so it takes 50k of ram
B> K> away from EVERY dos  window! But a .pif file can set up a
B> K> dos window to have any amount up to  a meg of XMS memory
B> K> available to the application in that window.
B>
B>NOS uses neither XMS nor EMS.  What it can use is the EMS page frame.  This is
B>very different from ordinary EMS-using programs, and is usually incompatible
B>with them.  EMS does provide for saving and restoring state around task
B>switches, even from inside TSRs, but NOS does not implement any of that.
B>

   Last time I looked at the JNOS source, EMS was used as pagable
memory.  However, the only use for EMS is to save screens for screen
swaps (ie multiple consoole sessions).  The screen save restoroe
code is very self contained and required little changes to support
the change (screen alloc, screen save, screen restore, and screen
free on session kill).

B> K>   I am incapable of making the changes necessary to allow
B> K> use of  XMS memorry so am asking that one of you good
B> K> programers take this on as  a task. I know many nos users
B> K> will thank you for getting this fixed.
B>
B>It is a major piece of work to use paged memory of any kind.  EMS is paged
B>through a frame window fixed in size and position, while XMS is copied back an
d
B>forth into a settable window.

Someone had started a XMS screen swap also, picking up a binary
only libary from somewere to do the actual copy requests.   I don't
think it was ever debugged and may not be complete; hence the advise
not to use it.

Although many HAMs use DOS, there are an increasing number of
programmers going to UNIX type systems like LINUX.  Development
for DOS systems is becoming a "enable for your friend" or "what
can I do with my old junk AT" type of endeavor.

NOS will use as much memory as DOS will allocate to it.  Some have
increased DOS memory by disabling vga modes and using page A0000
as regular memory.  Has anyone looked at what it would take to use
dos UMBs like loadhi tsrs do?  (ie try to allocate those and stick
them in the free list?)

milton
--
Milton Miller  KB5TKF  miltonm@bga.com